Abstract—In wireless networks, managing an increasing number of users becomes increasingly challenging as user density rises. To address these challenges, various algorithms are employed to divide users into smaller, more controllable groups. This approach is crucial for optimizing the performance of Non-Orthogonal Multiple Access (NOMA) systems, which are a key component of nextgeneration wireless networks like 5G and 6G. User grouping schemes in NOMA systems are essential for optimizing resource allocation, mitigating interference, improving spectral efficiency, ensuring fairness, and reducing complexity. As wireless networks evolve, particularly with the integration of advanced technologies like Coordinated Multi-Point (CoMP), Internet of Things (IoT), Millimeter- Wave (mmWave), Terahertz (THz), Unmanned Aerial Vehicles (UAVs), Multi-Input Multi-Output (MIMO), and 5G-6G, effective user grouping will become increasingly critical. This research paper provides a systematic classification and analysis of various user grouping schemes, offering valuable insights for enhancing network performance in next-generation wireless networks.